The role of the GATA transcription factor family in hematopoiesiscontinues to be a major focus of our research. Gene targeting experiments in mice by several laboratories have established that GATA-1, -2, and -3, are critical to blood development. While these factors recognize the same DNA site and sometimes coexist in the same cells, interestingly they do not compensate for the loss of one another. GATA-1 and -2 can interact with a group ofdouble GATA binding sites which exist in the regulatory regions of many critical genes, and in the beta-globin locus control region. While most GATA/DNA interactions are mediated through the C-terminal zinc finger,these double site interactions involve both zinc fingers, and the activity of these proteins varies in a binding site dependent manner,suggesting allosteric regulation. We have shown that these activity differences are not due to differential DNA bending, since the N-finger of GATA-1 does not contribute to that process. Because the N-finger of GATA-1 supplies the interaction surface for several critical cofactors,we suspect that the differences in activity may be mediated through site dependent conformational changes in the proteins that alter their interactions with these cofactors. We are attempting to solve the structure of the zinc fingers of GATA-1 bound to several double DNA sites, and are studying the activity of mutant GATA proteins to test this possibility. Other studies have shown that the chicken folate receptor gene andthe genes in the adjacent beta-globin locus are all regulated by GATA factors,but these genes are not expressed in the same temporal pattern during red cell development; the basis for this discrepancy is under investigation. The chicken beta-globin insulator element, which separates these loci maybe responsible, and/or there may be cis-elements in the individual loci which respond differently to the presence of GATA proteins. - GATA family gene expression development hematopoietic cells GATA-1 chromatin locus control region GATA-2